What is the aircraft in this photo? My great uncle is in the back row second to the right. He was born in 1900, so I think this photo is from around 1920. I think he was based at Kelly Field in San Antonio, TX. Does anyone know more about the aircraft or the group in the photo?
The close proximity between the pilot cockpit (the front cockpit) and the observer-gunner cockpit (the rear cockpit) suggests a Airco/ De Haviland DH-9A. On the related DH-4, the two cockpits were much further apart, with a fuel tank in between them.
Addendum-- "1,538 DH-4s were modified in 1919-1923 to DH-4Bs by moving the pilot's seat back and the now unpressurized gas tank forward, correcting the most serious problems in the DH-4 design." -from the National Museum of the United States Air Force website (link previously shared by ASE contributor JonSG). Since the DH-9A was not widely used in the US, the aircraft is in fact most likely a DH-4B.